1. Field of the Invention
The present invention relates to a drum unit for receiving bulk material for surface treatment, including a drum having jacket walls which end at both sides at a end disk, of which one jacket wall is designed as a lid which can be opened and closed for a charging of and a discharging from the drum.
2. Description of the Prior Art
Such drum units are used in the industrial field of surface treatments, e.g. for an electroplating, pickling, phosphating, cleaning, generally depositing a coating onto articles. Such articles are generally structures which can be handled as bulk material, such as articles like metal fittings, nuts, threaded bolts, further articles which are used in the electronic industries, articles for watches and also for jewelry.
In addition to a depositing a coating onto articles, drum units are also used in connection with a rinsing and drying of the articles. A drum unit includes besides e.g. a driving motor and its controls, drive transmission members, structures for the feeding of electric power, a drum for the receipt of the commodity to be treated which in operation rotates of a low speed. The walls of the drum may be of a screen like design or also may be designed with perforations, depending from the treatment to be made-of the respective articles. These drum walls may, furthermore, have a curvilinear, rectilinear or also an angular cross-sectional shape.
The drum jacket walls may also be designed in such a way, that the drum has a triangular cross-sectional shape with rounded corner areas, which drums are also designated as delta drums. The drum jacket walls may also be arranged in a rosette-like manner, such as is the case of semitube drums.
At least one of the drum walls or a segment of the drum jacket, resp. is designed as a lid, which can be opened for charging and discharging the drum, and is shut, closed during the treatment. The charging of the drum can proceed either manually or by a charging apparatus. The discharging of the drum may also proceed manually, or then so, that the drum having its lid opened or removed is rotated into a discharging position, possibly by a reversing of the rotation of the drum, so that the treated articles may fall into a collecting bin.
Until these days the opening and closing of the lid was accomplished manually or by special automatically operating apparatuses.
In case of a manual operation the locking of the lid is achieved for instance by locking clamps or locking straps, which is considered as a laborious task and in addition gives rise to the danger in that the operator may contact a treatment medium which is harmful to the human skin. Automatically operating apparatuses for an opening and a closing of the lid are expensive, require a lot of space and may also suffer break downs.
The DE-A-1 546 154 discloses a drum for the treatment of bulk material having a lid for a charging or discharging of the drum, arranged at a sidewall of the drum which orbits when the drum is rotating. The lid is pivotable parallel to the axis of rotation of the drum. The lid includes at one of its longitudinal edges a lever and a guiding roller, which cooperates with a cam disk which, is rigidly mounted to the frame of the drum. The key ring like cam portion included two end areas, which are at a distance from each other due to an opening acting as control recess.
The shape of this cam disk necessitates, however, that the lid must have the lever with the guiding roller, which parts increase costs, are prone to failures and their mounting is quite consuming. Furthermore, this cam part does not allow a direct safe complete opening of the lid, so that it is possible that specifically during the discharging a certain amount of the commodity which has been treated can be caught between the only partly opened lid and the inner side of the drum.
Hence, it is a general object of the present invention to provide a drum unit for receiving bulk material for surface treatment which includes a drum with a lid to be opened and closed which is supported to freely pivot around a pivot axis, which drum includes at least one cam disk which is operative to control the pivotal position of the lid, whereby any pivotal position of the lid is determined exclusively by its force of gravity and by the cam disk, so that the lid opens and closes by itself on its own exclusively dependent from the rotational position of the drum.
A further object of the invention is to provide a drum unit for receiving bulk material for surface treatment, including a drum having jacket walls which end of both sides at a end disk, of which one jacket wall is designed as a lid to be opened and closed for a charging and discharging the drum, which lid is supported at one of its longitudinal edges for a pivoting around a pivot axis which extends parallel to an axis of rotation of the drum, which drum includes at least one stationary cam disk for a controlling of the rotational position of the lid, which lid has at least one guiding portion adapted to co-operate with mentioned at least one stationary cam disk, which at least one stationary cam disk has a circumferential portion which has the shape of a circular arc and has a first end area and a second end area, which end areas are located at a circumferential distance from each other; and has further a control recess having a first and a second end, which ends are located at a circumferential distance from each other, which first end is shaped as a lid blocking surface; which lid blocking surface is followed in turn by a first, approximately rectilinear transition portion which extends up to the first end area of the circular arc shaped circumferential portion; and having a second, approximately rectilinear transition portion following the second end of the control recess and extending up to the second end area of the circular arc shaped circumferential portion.